In the prior art electronic expansion valve, utilizing the operating principle of a step motor, a magnetic rotor is driven to rotate by a coil, and the rotation of the magnetic rotor is transferred into an up-down movement of a leading screw, which drives a valve needle connected thereto to move upward or downward, thus the flow of the electronic expansion valve can be controlled.
The prior art electronic expansion valve has a main structure including a jacket, a valve seat, a magnetic rotor, a nut, a leading screw, a valve needle and a valve needle sleeve, etc. The leading screw is mated with a folding edge on the upper end of the valve needle sleeve by a fixing plate provided on the leading screw, so that the leading screw is movably connected with the valve needle sleeve; and the valve needle sleeve is fixedly provided with a valve needle at its lower end, thus a movable connection is achieved between the leading screw and the valve needle. The valve needle sleeve is provided with a spring therein, which has its one end abut against the fixed plate and the other abut on the valve needle. Thus, a certain pressure is established between the leading screw and the valve needle by the spring. When the valve needle is driven by the leading screw to move downward to close a valve port on the valve seat, the spring will be compressed by the leading screw after the valve needle contacts with the valve port, so that a certain pressure is established between the valve needle and the valve port, preventing the valve needle from being opened by the impact of liquids.
During the implementation of the present invention, the inventor found that at least the following problems are present in the prior art: in the prior art, due to the fact that the pressure of the spring is large, there still exists the pressure of the spring between the leading screw and the valve needle after the valve needle is driven by the leading screw to leave the port. Because of the large spring pressure between the leading screw and the valve needle, when the valve needle having left the valve port deviates relative to the leading screw, the valve needle thus deviated cannot easily be adjusted and restored under the action of the spring pressure. Moreover, when the valve port contacts with the valve needle, the friction surfaces between the leading screw and the washer and between the valve needle sleeve and the washer are large, and the arm of the friction force is also large, so that the leading screw can only rotate relative to the valve needle by overcoming a relatively large friction resistance, leading to difficulty in the relative rotation between the valve needle and the leading screw. Therefore, the prior art electronic expansion valve has poor reliability.